XDr, HG-EV, Microspline and XD are the four major freehub driver body standards that determine what kind of cassette you can use.
When replacing driver bodies, make sure the one you get is compatible with your hub model. For example, DT Swiss 350 and DEG 90T use different freehub bodies.
XDr: SRAM 12-speed road groups
HG-EV: Shimano 11/12 speed road cassettes.
Microspline (MS): Shimano 12 speed mountain groups
XD: Used on SRAM 12 Speed mountain cassettes.
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